Method of and apparatus for dehydrating liquid products



J. M. HALL Filed July 2, 1941 2 Sheets-Sheet 1 INVENTOR. Josg o/b M HallBY M ATTORNEYS.

Sept. 5, 1944.

METHOD OF AND APPARATUS FOR DEHYDRATING LIQUID PRODUCTS J. M. HALL2,357,649

METHOD OF AND APPARATUS FOR DEHYDRATING LIQUID PRODUCTS Sept. 5, 1944.

Filed July 2, 1941 2 Sheets-Sheet 2 panying drawings, in which- PatentedSept. 5, 1944 METHOD or AND APPARATUS FOR DEHYDRALTING LIQUID PRODUCTSJoseph Hall, Chicago, 111., assignor to Drying & Concentrating DelawareCompany, a corporation of Application July 2, 1941, Serial No. 4001759BCla-ims.

This invention relates to dehydrating-systems and more particularly' toapparatus for dehydrating food and other products drying mediums.

One of the objects of the invention is the provision of a new andimproved dehydrating system that is flexible in its adjustments andthatis adapted to dehydrate liquid products having different characteristicsand that require radically difierent treatments.

Another object of the invention is the provision of a new and improvedsystem for dehydrating liquid products together with novel means forcontrolling the operation of the system. Another object of the inventionis the provision of anew and improved method of dehydrating liquidproducts whereby the dehydrated product may have the desired density andmay be ready for storage when the process is completed.

A still further object of the invention is the provision of a new andimproved dehydrating system that is inexpensive to manufacture, easilyassembled. eflicient in operation and that is extreme y flexible in itsadjustments and in its operation.

Other and further objects and advantages. of the invention will appearfrom the following description, taken in connection with the accom-Figal is a side elevation of the dehydrating system shown more or lessdiagrammatically, with parts broken away and parts in section;

. Fig. 2 is asection on the line 2-2 of Fig. 1 showing the distributorhead and associated pa i;

Fig. 3 is a section on the line 3-3 of Fig. 1;

Fig. 4 is a top plan view of the snails above the dehydrator chambershown in Fig. l; v

Fig. 5 is a section on the line 5-5 of Fig. 3;

Fig. 6 is a-diagrammatic plan view of a modified form of apparatus; and

. Fig. 7 is a further modified form of dehydratingapparatus.

In dehydrating liquid products in a system depending on a heated dryinggaseous mediumfor A removing the moisture from the sprayed particles ofthe product, there are numerous factors to be by the aid of gaseous foreit is sprayed into the dehydrating chamber.

If it is desired that the dehydrated product per volume shall weighvless, then the concentration is less so that the concentrate will have-alow degree of concentration; that is, a small age only of the moistureis removed.

The present system is so designed that it may be easily adjustedoroperated to meet these various requirements.

Referring now to the drawings, the reference character I" designates adehydrating system which comprises essentially a furnace I l for heatingthe drying medium, a concentrator or concentrator' chamber l2 forconcentrating the liquid product and a dehydrator or dehydrating chamberl3 for dehydrating the concentrate.

. The furnace H is provided with a combustion I chamber, a" burner I5for discharging a combustible mixture of liquid fuel and air into thefur nace where it is ignited and burns in the usual manner. The furnace,if desired, may be provided with a forced draft comprising a blower [6,an intake conduit l1 through which combustion gases from the heatingchamber 18 pass into the fan.

These heated gases are discharged through the fan discharge conduit l9where they divide, a portion' going into the stack 20 and a. portionthrough the grates 2| into the combustion chamber M for increasing thevelocity of the gases of combustion through the heater and for minglingwith those gases whereby the temperature of the combustion gases issomewhat lowered whereby burning of the tubes is prevented. The passageI8 is provided with-a gate or valve 22 for varying the amount of thegases diverted into the stack 20 where theyare conducted to the exteriorof the system. The fan is so constructed that fresh air may also enterthe intake thereof, as is usual in such constructions.

Sin'cathe specific construction of .the heating system constitutes nopart of-the present invenv tion, it isnot thought necessary toillustrate or considered. In dehydrating some products, such .as citrusjuices, the humidity of the gaseous medium employed must be low while,on the other hand, in dehydrating other liquid products, such as glues,gelatins, resins and certain chemicals,.

the humidity may be relatively high. Again, the treatment of any liquidproduct will vary depending on the weight desired for a given volume ofthe dried product. For instance, if milk be dehydrated and the driedparticles weigh a given amount per quart and it is desired that theweight describe the same more in detail further thanto state the gate orvalve 22 may be adjusted to any desired position for dividing thedischarge from the fan to direct a portion or all up the stack and apart or none along the conduit l9 into the combustion chamber.

Mounted in the upper portion of the furnace l l is a heatingdevice' orheater 2 which comprises a casing 25 having the perforated end.

walls or flue sheets 26 and 21. Secured in theend walls or flue sheets26 and 21 are a plurality of flues or tubes 28 through which the dryingfluid flows, as will presently appear.

A baflle 29 may be-provi ded in the casing or chamber 25 for divertingthe heated gases from the combustionchambe I4 and which pass upwardlythrough "the grill ll upwardlyabove the baflle 29. These gases thenpassdownwardly percentaround the front portions of the tubes 28 andoutwardlyto the fan through the conduit |1.

Suitable means are provided for conducting a gaseous drying medium, suchas air, through the heater 24. As shown, a blower 32 having a fresh airintake conduit 33 and a discharge conduit 34 is provided for thispurpose. The conduit 34 conducts the air to the heater and after the airpasses through the tubes 28, I it passes into the conduit 35 whichconducts the heated gases to the dehydrator l3, and to the concentratorl2;

The upper end of the intake conduit 33 is, preferably, though notnecessarily, provided with a screen or filter 36 through which fresh airis adapted to enter. A valve 31 is provided for controlling the amountof air entering the fan through the conduit 33.

The conduit 35 is provided with a branch conduit 38 for dividing the airthat flows along the conduit 35 and for conducting this portion of theair from the heating unit or heater directly to the concentrator l2.

The section 4| of the main conduit 35 that extends beyond the 'junctureof the branch conduit 38 is provided with a valve 39 for controlling theamount of air admitted to the dehydrator |3. The valve 39 is soconstructed that it may entirely close the portion 41 of the conduit 35i that contains the valve.

The branch conduit 38 is also provided with a valve 42 which may beadjusted to either close the conduit 38 or admit the desired amount ofair to flow past the valve.

The extension 4| of the conduit 35 is connected to a snail 43 mounted onthe dehydrator i3 and which directs the air downwardly in a spiral intothis dehydrator chamber.

The dehydrator l3 comprises an upper section 44 and a lower section 45.The upper section 44 has an upper cylindrical portion 46 and a lowertapered portion 41 which is integral with the upper end of the lowersection 45. The section 45 comprises an upper portion 48 that flaresupwardly and merges into the lower portion 41 of the upper section and acylindrical portion 49 integral with the tapered portion 48. The lowerend of the lower section 45 is tapered downwardly as at and merges witha conduit 52 through which the dehydrated particles are discharged fromthe dehydrator by a valve 53 operated by a motor 54 in the usual manner.

The lower section 45, being of considerable smaller diameter than theupper section, functions as a very efficient device for-separating theproduct from the drying medium by centrifugal force due to the increasein the speed ing medium as a result of narrowing the inclosure and ofadding fresh air tangentially to this section, as will presently appear.By lengthening the cylindrical portion 49,- the efficiency of the lowersection is increased.

A conventional power operated screen 55 is provided below the dischargevalve 53 and through which the dried particles are caused to pass and bedischarged into a suitable receptacle 56 in the usual manner.

Since the details of the screen 55 and the valve .53 constitute no partof the present invention, it is not thought necessary to illustrate ordescribe the same more in detail.

The upper section 44 of the dehydrator l3 has its upper wall slightlydepressed and is provided with an axial opening in which a short conduit51 is secured. The upper end of the conwhere it is heated, 1

of the dry- 1 duit 51 has attached thereto the lower Wall of the snail43 of the extension conduit 4| so that the air passing along theextension 4| into the snail 43 will be directed downwardly in a spiralthrough the conduit 51. A discharge conduit 58 for the drying medium isprovided for the dehydrator chamber l3 and the same is arrangedconcentric with the conduit 51. As shown, the discharge conduit 58extends axially upwardly through the conduit 51 and is spaced inwardlyfrom the conduit to form an annular passage 59 through which the gaseousdrying medium passes from the snail 43. The conduit 58 extends upwardlythrough the extension conduit 4| and terminates in a snail 6| throughwhich the air passing upwardy through the sleeve 58 may escape from thesnail 6| into the branch conduit 38, as shown more clearly in Fig. 4 ofthe drawings.

It will thus be seen that the gaseous drying medium will pass into thedehydrator l3 through the extension conduit 4| and passage 59 and thatthe same will move spirally downwardly within the chamber and then willmove spirally upwardly in an inner spiral through the conduit 58 incontact with the outer spiral into the snail 6| and escape outwardlyinto the branch conduit 38.

As shown more clearly in Fig. 4, the gaseous dryingmedium that passesthe valve 42 direct from the heater 24 will pass along the conduit 38tangent to the snail 6 and will mingle with that discharged from thedehydrator l3 and be carried over to the concentrator l2. By means ofthese valves 39 and 42, the temperature of the drying medium passinginto the concentrator [2 may be varied as desired or as r"quired by t eliquid product that is being treated.

The outer spirally moving drying medium will tend to reverse at thejunction of the sections 41 and. 48 but in order to insure the continueddownward movement of the outer spiral into the lower section 45,suitable mechanism is provided. As shown, the lower portion of thedehydrator chamber l3 has mounted therein a short conduit 62 which isarranged axially of the dehydrator chamber. A hollow cone-shapeddeflector member 63 is rigidly attached to.the upper portion of theconduit 62 and extends downwardly to a position adjacent to the lowerwall 64 of the upper section of the dehydrator chamber thus forming apassage 65 beneath the deflector member 63 through which the airconstituting the outer spiral may flow downwardly into the lower section45 of thechamber.

The conduit 62 and deflector member 63 are supported in operativeposition by any suitable means such as the brackets 66.

In dehydrating liquid products that are not ,afiected by comparativelyhigh temperatures, the

drying medium employed may be heated to the most efiicient temperatureand in that event, it is desirable that the powder or dehydratedparticles be cooled before they are stored for future use. In theconstruction shown, suitable means areprovided for introducing a streamof cool air into the lower section of the dehydrating chamber forcooling the product. -As shown, a blower 61 operated by a 'motor 68delivers fresh air through a' conduit 69 tangentially into anintermediate portion of the lower section 45. This air will not onlylower the temperature of the particles but, being comparatively dry,will also lower the relative humidity of the air within the chamber.

The concentrator or concentrator chamber I2 is of the cyclone type andcomprises an'upper cylindrical section 60 and a lower tapered secsection38 is connected tangentially to the snail 14 in a manner similar to theconduit 4| and The upper portion 68 of the con-.

.The lower portion of the section snail 43 of the dehydrator 3. In otherwords,

the drying medium passing from the dehydrator I3 and from the heater 24is conducted along the conduit 38 into the snail 14 which causes thesame to move downwardly in a spiral and within the concentrator chamberl2.

A conduit 15 is provided which is coaxial with the conduit 13 forconducting the drying medium from the concentrator l2. The conduit 15extends upwardly through the snail 14 as shown in Fig. -1 of thedrawings. This conduit is of less diameter than the conduit 13 toprovide an inlet passage 16 around the conduit. 15 for the dryingmedium-entering the concentrator. A snail 11 is provided on theupper'end of the conduit 15 above the snail 14 for directing the dryingmedium laterally into a return conduit 18. The return conduit 18 is incommunication with the upstanding conduit 33 which, in turn, is incommunication with the intake 19 of the fan 32. a

Under certain conditions, it may be desired that none, or only part, ofthe drying medium from the concentrator |2 be returned to the fan 32.for varying the amount of drying medium recirculated. As shown, conduit18 is provided with a valve 8| which may be adjusted to any posi-' tionbetween fully opened and fully closed positions. When in fully closedposition, none of the drying medium from the concentrator will bepermitted to 'ente'r the intake of the fan. A discharge passage 82having an adjustable valve 83' therein may be provided through which thedrying medi m from the concentrator chamber l2 may be charged from thesystem. When the valve 8| is entirely closed, the valve 83 is fullyopened and vice versa, so that all, or none,

of .the drying medium passing through the con- -duit 18 will bedischarged through the conduit 82. If only a portion of the dryingmedium is to be discharged to the atmosphere, both valves will bepartially open, as will be evident from an in-- spection of rFig. 1.

Suitable means are provided for supplying.

the liquid product to the concentrator chamber l2 and the concentrate tothe dehydrator I3. As shown, the liquid product is contained in areservoir 84 and means are provided for delivering the same to aspraying mechanism or spray Suitable valves are therefore provided head85 located within the upper portion. of the concentrator l2.

The reservoir 84 may be so mounted that the liquid will be delivered tothe spraying mechanism by gravity or, as shown, a pump 86 may beprovided for delivering the liquid to the spraying mechanism. Thespraying mechanism 85 is substantially like that shown in my Patent No.2,287,795,issued June 30, 1942, for Mechanism for removing moisture fromliquid products. Since 'the details of'the spraying mechanism constituteno part ofthe present invention, it is not thought necessary tospecifically concave on its outer surface.

illustrate or describe the same further than to state that the hollowrotating shaft 81 sunrounded by at protecting sleeve I81 extendsdownwardly into the upper portion of the concentrator I2 and has anaxial passage 98 for conducting the liquid product to the spray head.

This rotating shaft may be, and preferably is,

an extension of the armature shaft of a motor '88 mounted on the snail11. The lower end of ed together by arim which assists in rigidifyingthe structure and forms an annular deflector 92,

The nozzles 9| extend outwardly beyond the concave surface of thedeflector and are detaohably connected to said arms. The nozzles aredetachable so that they may be replaced by nozzles having larger orsmaller bores therethrough as required by the particular liquid productthat is being treated. If the liquid is thin, nozzles with smaller boresare employed.

The shaft 81, and with it the head 85, is adapt-' ed to be rotated atcomparatively high velocity by the motor 88 and the liquid to beatomized is conducted by pipe 93 to the'hollow shaft 81 by the pump 86.This.-liquid passes downwardly through the shaft 81 into the head 85 andis thrown'outwardly by centrifugal force through the nozzles 9| in theform of a spray into the drying medium passing downwardly through thepassage 16. The head 85 rotates in the same direction as the spirallymoving drying medium and, consequently, assists in the rotation of saidmedium. This gaseous drying medium rotates spirally downwardly tothebottom of the concentrator in an outer spiral and then reverses its*direction and moves upwardly in an inner spiral container 94 from whichit is conducted by a pipe 95, with the aid of a pump 98, to thedehydrator l3. The dehydrator i3 is provided with a spray mechanism 91similar to the spray mechanism 85 of the concentrator l2. Since thespray mechanism and cooperating parts are substantially the same as thatalready described, it is not thought necessary to 'repeat thedescription at this point.

Within the dehydrator I3, the cancentrate or concentrated liquid fromthe container 94 is sprayed into the outer'spiral of the drying mediumwhere the moisture is removed and the dried particles are thrown bycentrifugal force against the walls of the dehydrator and slidedownwardly alone said walls to the discharge conduit at the bottom ofthe cabinet. Any impalpable particles of material that'ar carried overinto the inner spiral, are 'thrownputwardly by the inner spiral intothis outer spiral and by the outer spiral thrown outwardly against thewalls of the cabinet.

In Fig. 6 is shown a modified form of the construction. In this form ofthe device, the dehydrator chamber I3 and the concentrator chamber I2are the same asthat already described. Likewise, the heater 24 andfurnace II may be the same as that disclosed in Fig. 1.

In this form of construction, air is employed as the heating medium butit is not recirculated through the system. Air enters the fan 32 throughthe conduit IOI and the discharge conduit 34 of the fan conducts the airto the heater 24 in the manner already described. The conduit IOI mayhave a screen or filter I02 in its outer end for cleaning the airentering the system. A valve I03 is provided in the conduit IOI forcontrolling the amount of air entering the fan 32. The fan is adapted tobe operated by a suitable motor I04. A conduit I05 conducts the heatedair from the heater 24 and this conduit I05 is divided-one section I06conducts a portion of the heated air directly to the snail I07 of theconcentrator I2 while the other section I08 conducts the air to thesnail I09 above the dehydrator I3.

Sections I06 and I08 are provided with suitable valves I and H0,respectively, for controlling the amount of heated air passing from theheater through these branch conduits. The heated air from the dehydratorpasses through a conduit I II to the snail I01 where it merges with airpassing through the conduit I06 into the snail I01. The heated air fromthe concentrator I2 passes outwardly through a' conduit II2 into theatmosphere.

The form of the apparatus shown in Fig. 7 difiers from that shown inFig. 6 in that it may be so adjusted as to form a closed system for thecirculation of the heated gaseous drying medium. In this form of device,the heater 24, which may be the same as that disclosed in Fig. 1, isadapted to heat the drying medium as it passes through from the fan 32,as in theprevious constructions. The fan discharges through conduit I I3into the heater and the discharge conduit I I4 from the heater dividesone branch H delivering the drying medium to the snail I of thedehydrator I3, while the other branch II6 delivers the gaseous dryingmedium to the snail I of the concentrator chamber I2.

The drying medium from the dehydrator I3 is conducted along a conductorII'I into the snail.

I30 where it merges with the drying medium passing along the conduit H6.The drying medium discharged from the concentrator passes along conduitII8 back to the fan 32, thus completing its cycle of circulation. v

The conduit IIB may, if desired, be provided with a discharge conduitI2I having a valve' I22 therein for controlling the amount of dryingtheis provided in the conduit III between the dedium discharged throughthe conduit I2I to the 1 atmosphere. A valve I23, between the fan 32 andthe conduit -I2I, may also be provided in the conduit II8 forcontrolling the amount of the drying medium delivered back to the fan32.

The conduit II8 may be provided adjacent to the fan 32 with an intakeconduit I24 for said fan whereby. fresh air may be introduced into thesystem. This conduit may be provided with a -valve I25 for controllingthe amount of fresh air introduced into the system as-in theconstruction shown in Fig. 1.

A discharge conduit I26 may be provided in the conduit Ill whereby, ifdesired, the drying medium from the dehydrator I3 may be discharged inwhole or in part into the atmosphere.

A valve I2'I is provided in the conduit I26 for con- 76 hydrator I3 andconcentrator I2 for controllin the amount of air passing to theconcentrator from the dehydrator chamber.

The spraying of the product and the means for conducting the same fromthe reservoir of the concentrator and to the dehydrator are the same ashave been described above. It is not thought necessary to duplicate theillustration or to re- ,peat the description of this feature of theinvention at this point any further than to state that if thedehydrators I3 are used alone without previously concentrating thematerial, the liquid product supplied to the dehydrator is placed in thereceptacle 94 to start with.

It will thus be seen that with this latter construction, theconcentrator and dehydrator may be operated independently or together asoccasion may require. It will also be noted that in all iorms of thedevice, provision is made for dividing the gaseous drying medium fromthe furnace in any desired proportions as required by the particularproduct treated or for obtaining a product of the desired density. 7

Since the operation of the dehydrator, concentrator, fan and heater,shown in this construction, is the same as that previousl described, itis not thought necessary to repeat a description of the operation of thesystem with reference to this construction.

The amount of moisture left in the liquid prod uct after passing throughthe concentrator chamber l2 may be varied by varying the temperature ofthe drying medium or by varying the amount of heated air diverted to theevaporator chamber or by varying the amount of the product delivered tothe chamber. 7

Substantially the same method may be employed for treating the productin the dehydrator chamber I3.

In varying the amount of liquid product delivered to the two chambers,the pumps 86 and "96 may be of the variable type or valves I30 ing theirdehydration. In order to preserve the.

vitamins in certain products and, prevent oxidation or chemicaldecomposition in others, it is imperative that the temperatures withinthe drying chambers be closely controlled. It has been found that withthis system, the temperature of the drying medium may be above whatwould be expected because of the temporary character of the exposure andthe cooling efiect of the evaporating moisture. In practice, in theoperation of the system, the operator, in starting, brings the dryinggaseous medium up tothe desired temperature and during the operation ofthe system, the temperature of the dehydrating chamber is maintained ata substantially constant temperature by controlling the feed of the pumpthat supplies the concentrate thereto. Likewise, the temperature of theconcentrating chamber may be maintained substantially constant bycontrolling the feed of the pump that supplies the liquid produnderstoodthat the same may operate as a, concentrating device with a concentratedliquid instead of a dry powder as the final product.

The terms concentrator and dehydrator" are used for convenience inidentifying the parts and are not necessarily intended as words oflimitation since the claims are intended to be construed as broadly asthe state of the art will permit.

It is thought from the foregoing, taken in connection with theaccompanying drawings, that the construction and operation of my devicewill be apparent to those skilled in the art and that changes in size,shape, proportion and detail may be made without departing from thespirit and scope of the appended claims.

I claim as my invention:

1. In a system for dehydrating a liquid product, a heater, aconcentrator chamber, a dehydrator chamber, a. fan, a conduit forconducting a gaseous drying medium to said heater from the discharge ofsaid fan, means for conducting said medium from said heater and fordischarging the same through an axial opening only into said chambers inseries, means for bypassing a part or all of said medium around saiddehydrator chamber to said concentrator chamber, means for conductingsaid drying medium from said concentrator directly back to said fan,means anterior of said fan for discharging a variable portion of saidmedium into the atmosphere, means for spraying a liquid product intosaid medium as it enters axially into said concentrator chamber, meansfor spraying the concentrate from said concentrator chamber into saidmedium as it enters axially into said dehydrator chamher; and means forintroducing a current of cool air into the lower portion of saiddehydrator chamber for cooling the dehydrated material and 'the mediumbefore they are discharged from said last-named chamber.

2. A method of dehydrating a liquid product which comprises heating adrying medium in a dehydrating system, dividing the medium, causing oneportion thereof to flow in a downwardly moving outer spiral into adehydrating chamber and then in an inner upwardly moving spiral fromsaid chamber, then mixing the last-named drying medium with the otherportion of the first-named medium and causing the mixture to movedownwardly in an outer spiral in a second dehydrating chamber and thenupwardly in an inner spiral out of said second chamber, then discharginga repeating the process in one continuous operation and simultaneouslyspraying a liquid product into Y the outer spiral of .the' drying mediumin the amounts of the product and concentrate sprayed into said chambersand the relative amounts of drying medium and air discharged andintroduced into said systems 4. In a system for dehydrating a liquidproduct, a heater having a gas inlet flue and a hot gas outlet flue, aconcentrating chamber having a hot gas inlet and a hot gas outlet, adehydrator chamber having a hot gas inlet and a hot gas outletconcentrically arranged at the top of said chamber, branch conduitsconnected 'to the heater outlet flue and to the dehydrator chamber inletand outlet respectively, a conduit connecting the dehydrator chamberoutlet with the concentrating chamber inlet, a conduit connecting theconcentrating chamber outlet with the heater 1 portion of the mixtureinto the atmosphere, adding air from the atmosphere to said mixture,

inlet flue, a valve in each of said branch conduits for controlling theproportion of hot gas direct from the heater and that discharged fromthe dehydrato'rqzhamber which are mixed in the conduit connecting thetwo chambers, and means for spraying a liquid product first into theconcentrating chamber and then into the dehydrator chamber;

5. In a system for dehydrating a liquid product, a pair of evaporatingchambers for removing moisture from a liquid product, a heater, 2, fan,means for conducting a gaseous drying medium from -said fan through saidheater to said chambers, means for causing said drying medium to fiowfirst spirally downwardly in said chambers.

from the heater to one chamber, means for mixing the remainder of themedium delivered by said' heater with the medium discharged from thelast named chamber and for delivering the mixture to the other chamber,means for selectively varying the proportion of medium delivered to saidone chamber, means for spraying a liquid product into said medium withinsaid chambers for removing the moisture therefrom, and means for causinga portion only of said medium to be recirculated through said heater.

6. A method of dehydrating a liquid product which comprises heating adrying medium in a dehydrating system, dividing the medium, causing oneportion thereof to flow down into a dehydrating chamber andbe dischargedtherefrom, then mixingthe discharge with the other portion of thedivided medium and causing the mixture to move down into a seconddehydrating chamber and be discharged therefrom, discharging a portionof said discharge to the atmosphere, returning the remainder to beheated and recirculated,

, y 3. In a system fordehydrating a liquid product,

a heater having a gas inlet flue and a hot gas outlet flue, aconcentrating chamber and a dehydrator chamber each having a hot gasinlet and a hot gas outlet, branch conduits connectedto the heateroutlet flue and to the dehydrator adding air from the atmosphere to themedium in one of said chambers, spraying a liquid product into themedium in the second-named chamber,

spraying the concentrate into the medium in the first-named chamber andremoving the dehydrated product therefrom, and regulating the relativequantities of medium in said two portions and the amount of mediumdischarged from and air added to the system so as to control thespecific gravity of the dehydrated product.

JOSEPH M. HA L.

